The present invention relates to medical devices. More particularly, the invention relates to a filter that can be percutaneously placed in a blood vessel, such as the vena cava of a patient, to capture clots.
Filtering devices are widely utilized for protection against potential pulmonary thromboembolism (also referred to as PE) in at-risk patients. A need for filtering devices can arises in for example trauma patients, orthopedic surgery patients, neurosurgery patients, or in patients having medical conditions requiring bed rest or non-movement. During such medical conditions, the need for filtering devices arises due to the likelihood of thrombosis in the peripheral vasculature of patients wherein thrombi break away from the vessel wall, risking downstream embolism or embolization. For example, depending on the size, such thrombi pose a serious risk of pulmonary embolism wherein blood clots migrate from the peripheral vasculature through the heart and into the lungs.
A filtering device can be deployed in the vena cava of a patient when, for example, anticoagulant therapy is contraindicated or has failed. Filtering devices are either permanent or retrievable implants. A retrievable implant may be desirable so that a filtering device does not remain implanted in the patient for life, even though the condition or medical problem that required the device has passed. In more recent years, filters have also been used or considered prophylactically in preoperative patients and in patients predisposed to thrombosis which places the patient at risk for pulmonary embolism.
Currently available vena cava filters generally include a number of struts formed from individual pieces of wire arranged to give the filter its shape and collected at one end by a separate piece that gathers the ends of the struts together, such as a collet, a bushing, or a sleeve, generally referred to as a hub. Although these devices are effective, their construction could be simplified.
Moreover, although spiral-shaped filters are known, many of these suffer from low compressibility, and lack resistance to stress caused by compression from other portions of the body. Finally, some filters are susceptible to tilting or becoming off-center during deployment.
There is a need for filter devices which are simple to make and provide geometries that are efficacious for capturing emboli and clots.